Revert "Bump next from 15.5.10 to 16.1.6" #3587

Job	Run time
Set CI/CD metadata	6s
Commit stage / Count lines of code	9s
Commit stage / Lint, style and type check code	50s
Commit stage / Scan secrets	13s
Commit stage / Lint Terraform	1m 15s
Commit stage / Check Markdown format	7s
Commit stage / Check file format	7s
Commit stage / Check English usage	13s
Commit stage / Scan dependencies	38s
Test stage / Unit tests	1m 37s
Test stage / Static analysis	1m 19s
Build stage / Build and upload artefacts	2m 3s
Deploy action (main only)	2m 47s
Acceptance stage (main only) / Contract Tests on (dev)	37s
Acceptance stage (main only) / E2E Tests on (dev)	4m 2s
Acceptance stage (main only) / EliD API tests (preprod only)	0s
	16m 3s

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